The present invention discloses a solar radiation receiver, applicable to the conversion of solar energy into thermal and electrical energy. Its use has a relevant interest in the power generation industry.
Currently there are three big technologies exploiting solar energy to turn it into thermal and electrical energy, cylinder-parabolic receivers, tower solar system with heliostat field, and parabolic dishes. The present invention is centered in the latter technology, wherein solar radiation strikes on a paraboloid (a “parabolic dish”, that is usually a paraboloid with a circular section), and a heat machine is located at its focus. This heat machine is usually a perfected Stirling engine (initially described by Robert Stirling in his patent of 1816, see document GB 4081 A.D. 1816) which operates between a hot focus (a solar radiation receiver) and a cold focus. The mechanical energy that the Stirling engine or an equivalent engine, produces, actuates an alternator that generates electrical energy.
As aforementioned, in the systems with parabolic dishes the solar radiation is received on the receiver. Said receiver heats a working gas, which actuates the heat engine. For a given thermal energy, increasing the receiver performance involves increasing the working gas temperature, and consequently, increasing the engine performance. This causes the total performance of the machine to be more efficient.
The Stirling engines that have been used in these solar plants have utilized receivers formed by a tube bundle, which is located facing the paraboloid axis. However, in this configuration, the surface which has been used by the thermal energy coming from the concentrator (the parabolic dish), is only a percentage of the concentrator projection. Besides, the tube bundles that are used in the state of the art are devices made up of a plurality of pieces, which are welded to each other and to the collector. This type of welded construction generates, relatively often, mechanical tension problems when the device is subjected to thermal cycles, which many times result in material stressing and its subsequent breaking. On the other hand, it is quite common that those devices that follow the Stirling cycle use hydrogen as the working fluid to improve their performance. Given that H2 burns in contact with the air, the shapes provided for in the current state of the art imply a risk of fire and explosion.
To solve the aforementioned problems, the present invention proposes a solar receiver (that in some shapes it is flat, and in others it is not), that uses the entire projected surface of the concentrator, so the used area is maximum. Moreover, its construction is more robust and safer than the tube bundle solution that has been typically used up to now, since it avoids the currently existing problems arising from the welded joints of the different components.
Diverse shapes of solar receivers linked to Stirling engines are known in the current state of the art there. Thus, document GB 2296047 A1 describes a Stirling engine with a crankshaft over which a structure is assembled, and a series of flexible diaphragms defining the working chambers, hot and cold, wherein the working fluid flows, is linked thereto. Document CN 201433829 Y discloses a heat cavity absorber for the Stirling engine of a solar device, with U-shaped channels.
Document U.S. Pat. No. 4,114,597 A discloses a unitary solar collector for transfer of thermal energy which is a synthetic thermoplastic unit. The unit has a solar-energy transmitting region and a solar-energy absorbing regions. The unit is useful for heating purposes.
However, no device with the specific characteristics shown by the present invention has been disclosed.